Objective: To examine the etiology and clinical significance of elevated serum cardiac troponin I (cTnI) in patients with rhabdomyolysis.
Methods: Data on 91 (63 men) consecutive patients with rhabdomyolysis were examined.
Results: The mean age was 57.8+/-19.6 years (range 24-97 years). Patients were divided into two groups: cTnI-positive with serum cTnI >0.6 ng/ml (n=19) and cTnI-negative with serum cTnI <0.6 ng/ml (n=72). Prevalence of cardiovascular risk factors was equal in both groups. Illicit substance use was more common in the cTnI-positive group (31% vs. 14%, P=0.04). Peak creatine kinase (CK) was higher in cTnI-positive group (34,811+/-38,309 vs. 15,070+/-21,655 U/l, P=0.04) but there was no difference in the MB isoenzyme (CK-MB) (118+/-132 vs. 89+/-451 ng/ml, P=0.63). In cTnI-positive group, there was a strong correlation between peak CK and CK-MB (r(2)=0.606, P=0.00008) but not between peak cTnI and peak CK (r(2)=0.164 and P=0.08) or CK-MB (r(2)=0.134 and P=0.12) levels. Serum creatinine was higher in cTnI-positive group (3.58+/-2.73 vs. 1.83+/-2.01 mg/dl, P=0.02) but there was no correlation between serum creatinine and cTnI (r(2)=0.121, P=0.158). None of the cTnI-positive patient had segmental wall motion abnormalities. Seventeen (89%) patients in cTnI-positive and 19 (26%) in cTnI-negative group required admission to intensive care unit (P=0.0001). Hypotension (37% vs. 6%, P=0.0002) and sepsis (47% vs. 11%, P=0.0003) were more common in cTnI-positive group. Duration of hospitalization was longer in cTnI-positive group (17.7+/-11.7 vs. 8.9+/-13 days, P=0.007) but there was no significant difference in mortality.
Conclusion: In rhabdomyolysis, serum cTnI may be elevated unrelated to the degree of muscle damage, renal failure and cardiovascular risk factors, and is likely related to the etiology of rhabdomyolysis, as is evidenced by significantly higher serum cTnI with illicit substance use, hypotension, and sepsis. Elevated serum cTnI is associated with a higher morbidity.